wl12xx: don't indicate up PS-filtered dummy packets

Dummy packets are currently only sent on the system_hlid link. The
system_hlid link should never be filtered for PS (as it is not
a STA link). Even so, for correctness, don't indicate dummy packets up.
The skb does not belong to mac80211 and as such does not contain a
correct skb->cb.

Signed-off-by: Arik Nemtsov <arik@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>
diff --git a/drivers/net/wireless/wl12xx/tx.h b/drivers/net/wireless/wl12xx/tx.h
index 6519be4..5c0fbbe 100644
--- a/drivers/net/wireless/wl12xx/tx.h
+++ b/drivers/net/wireless/wl12xx/tx.h
@@ -214,5 +214,6 @@
 u8 wl12xx_tx_get_hlid_ap(struct wl1271 *wl, struct sk_buff *skb);
 void wl1271_tx_reset_link_queues(struct wl1271 *wl, u8 hlid);
 void wl1271_handle_tx_low_watermark(struct wl1271 *wl);
+bool wl12xx_is_dummy_packet(struct wl1271 *wl, struct sk_buff *skb);
 
 #endif